I need to get into building a PF spreadsheet and getting things in better order, but fwiw the way I sometimes frame the question of whether or not it's "okay" for me to buy something is 1) Will spending the money compromise or help my ability to pursue something else I want to do, based on the price and utility, 2) Could I buy 20 of them? Even better if I could buy 20 without tangibly hurting my wallet.

If you can buy 20, 1 is probably fine, don't stress too much.